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maddmike writes "High altitude kites could produce energy equal to some power stations at a comparable cost without polluting. The technique uses a thing dubbed a 'Laddermill' - a chain of kites attached together to create a loop in the sky more than 5 miles long."

The article doesn't say much about how such a structure could be maintained. How in the world could kites stay up for a long enough period to be feasible as a power source? Or is all this still in the "just five more years" phase?

Check out http://www.laddermill.com/. [laddermill.com] I think it will be awesome to see these generating a city's power one day.
Side note. Kinda funny how it is being developed for high altitude in the Netherlands.

The industrial world has a vested interest in maintaining itself and not destroying itself or us: If there is no civilization or people to buy goods and services, then money and soon power (as in power of the people, not nuclear power) go bye-bye.

It's simplistic and misses all those pesky nuances, but true.

Now, whether or not the industrial world _knows_ how to maintain itself and not destroy us... THAT's another question...

Actually, "industry" is only concerned with maintaining civilization and the environment to the BARE MINIMUM necessary to keep the masses consuming product. Industry can destroy and destroy, up to the point just before people can no longer consume.

I'd say at least in the USA, we have a long way to go before we hit the bottom.

Actually, "industry" is only concerned with maintaining civilization and the environment to the BARE MINIMUM necessary to keep the masses consuming product. Industry can destroy and destroy, up to the point just before people can no longer consume.

I'd say at least in the USA, we have a long way to go before we hit the bottom.

[On smoking]Ishmael: You should try to quit. They say its bad for your heart, your lungs. It quickens the aging process.Roy: Who's done more research than the good people at the American Tobacco Industry? They say its harmless. Why would they lie? If you're dead, you can't smoke.

Don't worry, if it's successful it's not pollution we'll have to worry about - it'll be the fact that they absorb all the energy of the wind, mess up the climate, and then cause all sorts of weather anomalies. Instead of global warming, we'll have...global "stasis?"

I hadn't even thought of that, but yes, we would likely screw something up with too many of them, as we would be leeching energy from one of the most important systems in the atmosphere. There's a lot of energy up there, but removing even small amounts might have pretty adverse effects.

I remember when wind farms started generating controversy - mainly by those bothered by sight of them (see Kennedy's and the Nantucket Sound controversy). Those type of folks have paid obscene amounts of money to stop things like the Cape Wind project. Their reasoning (besides ruining their view of the sound in the morning)? It kills birds, it might change the climate, etc. Yeah... And what about the two coal plants that currently provide them electricity? In comparison, what do THEY generate?!

So when I see possible energy solutions like this one, it makes me rack my brains to think what excuse will these NiMBY folks use THIS time? Thanks so much for 'global stasis'. I can see the lawsuits now...

I vote for moving the coal plants in CT that feed Nantucket down near the Kennedy Compound. You might as well get them closer to where the HOT AIR is generated...

How did this crap get modded up to 5?Wind is not finite or depletable.Wind is constinuously generated by the sun's differential heating of our planet.As the air warms, it expands and rises. As it cools, it contracts and falls down.We will never have "global stasis" and it would be hella difficult to globally impact the weather system.Global warming exists because gases travel and diffuse throughout the entire atmosphere.Windmills are fixed.Slowing down the wind a little bit here and there does not immediate

Flying kites at high altitude isn't as easy as it seem: pretty soon you get a lot of problem from the line(s), chiefly the weight of the line, but also line drag.

The former problem is essentially a strength vs. weight problem that even high tensile lines made of dyneema won't solve easily (above 400/500m, a 6m parafoil can very well sit there and refuse to climb with standard lines).

The latter problem introduces a problem of angle, since the line becomes curved under the wind drag, which makes the section right under the kite more and more vertical as it climbs, which in turn "flattens" its incidence angle and reduces its lift. It's always possible to modify the incidence on the ground to compensate, but takeoff can get dicey then. And of course, the wind drag on the line also tends to pull the kite down, and it's not negligible with a lot of line up.

So yes, it should be possible to use kites to generate power, but there will have to be a great deal of electronic magic to regulate everything, down on the ground and up in the air, if high altitude flying is to be more than stunts performed by enthusiasts on good days with (semi-)controlled conditions.

why not use the kites to collect solar energy? Although, I don't know how better/worse this would be, but it could free up a lot of land needed to maintain solar panels - and depending on how high the kites are, could they could collect energy in nasty weather!
With regards to aircraft, I'd say make these power-gathering areas no-fly zones -- otherwise how different is it from a field of broadcast towers?

What power stations are these? According to the article, a city like Seattle would require on the scale of a hundred thousand of these kites (or hundreds of plants with 400 kites each) to supply the city with electricity. And when you consider the limits to where these could be place (airspaces are out, along with any place where something could be damaged should one of these guys go down), this isn't a very feasible way to replace our current power system.

What they were saying was equal was the cost, not the total output per kite.

"And when you consider the limits to where these could be place (airspaces are out"

String them up all along the borders of the continental USA and it'd be a great bonus for homeland security. Keep those pesky terrorists out as well as those pesky tourists, heck its all 'stranger danger'!

These kites could never replace traditional (ie coal) plants anyways - they can't be flown during storms or when the wind is too calm, etc.

The benefit of these is that while they are flying, the coal plants don't need to work as hard.

The reference below describes each cable link being 200 meters. Thats one for every 2.2 American football fields or two Canadian footbal fields (excluding the end zones). If you put them too close together they start to interfere with each other. IIRC, traditional windmill

"Yes, the article was severely confusing. They claimed that a single Laddermill can produce 100 megawatts, but that Seattle would need a few hundred of them? The last I heard (2001), Seattle's power consumption was on the order of 1300 megawatts. That'd be only 13 Laddermills, not several hundred."

Yeah, I was wondering about that. But since these guys wouldn't be up all the time, that 100 megawatt output probably isn't continuous. I'm guessing that number is the amount needed in order to produce enough

TFA said the cable would let the kites fly five miles high - not that the cable was five miles long.

This means the cable is actually ten-plus miles long. I don't remember my differential equations from twenty years ago, but I do know that as the cable gets longer (goes higher), the amount of weight supported increases. So half the loop is a five mile strand going up, and the other half is five miles of cable coming down. It sure seems like the weight on the top kites would be extraordinary. Do we have carbon-fiber cable yet?

And what happens when lighting hits it? Didn't Tesla manage some stunning current with a structure less tall than this?

The cable has a series of kites attached, so that the kites on one side are providing just enough lift to support themselves and thier section of cable, while on the other side they are providing maximum lift, so the tension in the cable would be minimal at the top, maximum at the bottom of the cable on the lift side.

I had not made the conceptual leap that each cable segment was essentially being lifted individually, by its host kite. Of course, they are all tied together, which is where the power comes from. The weight problem isn't a problem - it is just 'overhead' so to speak.

Thank you too for the link. The cable will be made from Dyneema, the world's strongest fiber. [dsm.com] It is apparently a superstrong polyethylene fibre, which I assume means it won't conduct electrical strikes.

Why wait for lightning? I mean you could get a corona discharge of the thing, just off the earth's ambienent electric field. My Dad, who happens to be a physcist argues that the discharge would be about 1,000 volts per foot. The only reason you don't get a discharge with out a device like this is because the impedenace of air is too high. And if you make it out of something that is non-conductive, you managed to make a huge capacitor -- the wings would generate a huge electric charge, and everytime a wing came down it would arch to the nearest grounded object (aka the world's larges capacitor). In other words, you want this be conductive, just so you don't have some unlucky bi/quad-ped walking by to get zapped by some serious static electricity. Corona discharges would be _better_ since you could run it to ground -- but it brings new meaning to the term "hi-voltage" power lines.

The other problem is that the cable would have to, at a minium, support something on the order of 20,000 psi. The only way to offset that would be use hellium or some other lighter-than-air gas in the sails. However, then you have to put this thing under stress in order to generate the power, so were back to the 20,000+ psi range. Steal is pretty much out. What sort of fiber/metal/ceramic are thinking of?

I'm really picturing this being quite the Rube Goldberg contraption. Maintaining such a system of giant kites in such strong winds is going to be a problem, as is lightning, storms, etc.

The nice thing about some of the other alternative power systems is that they tend to be smaller scale and are backed up by the power grid or some other form of generation. If you have a 100MW kite system, it would be such a substantial source of power that providing a backup to it when there is no wind or the cable breaks, will not be trivial.

The article is very short on details. For instance, how will they obtain the the power if the kites are floating hundreds or thousands of feet in the air? Unless their tethered, in which case on whose land would they be tethered? And what would they do when the wind drops?

The inherent problems are astronomical - lift/weight ratio of kite-to-cable, vast amounts of airspace used etc. - but even the most basic feasibility requirements of this project cannot be met.

Have a look at some of the plans and protoype pics of this behemoth, and it becomes clear (if not in the article) that the intention is for the ladder to be ground-originated, not just ground-anchored. This means the kites are travelling up from the ground to 5 miles and back again. The volume occupied by such a structure - especially one as non-static as this - would be monumental, not to mention the massive safety margin required to have more than one in operation within a few miles of any other ladder.

So if we're looking at 400 ladders to generate enough to power a city, we're look at a good 3000+ square miles of land if we're to be sure that no ladder is to collide with another. Not practical on any scale, I suspect.

Now if we're to be sure the things don't come down every time there's a spot of bad weather, we are looking at getting them up above the common cloud-cover atmospheric strata. In that case, why the hell not just use bigger kites, no ridiculous ladder-arrangement, and use the kite-wing surface-area to convert solar-energy? If the kites are well-engineered and -controlled enough to be able to operate in such a stringently unified fashion, I'm sure the same technology could be used to keep solar-kites in the air. True, the strain on the cables would be even greater if they have to be reliable electrical conduits as well, but that's really only one of several major flaws in this project.

The idea of tethered high altitude wind power generation has been around for a long time. The people behind Sky Wind Power Corporation (http://skywindpower.com [skywindpower.com]) have been developing their technology since 1979.

They do not use kites but a tethered electrical generator, like a helicopter with 2 fifteen foot rotors and no cabin. The documentation on their site seems to cover a lot of questions that would come up here, especially about the tether etc.

It is just sad to see another australian inventor having to go overseas to try and get their idea noticed.

The numbers don't make much sense. 100 megawatts is about 75 MILLION horsepower, or about 35 BILLION pound/feet per second. It would take a HECK of a kite string, probably thicker than a suspension bridge cable, to bring down that much power.
Just supporting the cable is going to take a heck of a high wind.

oops, shouldnt try to do the math in my head.
Still, it's a whole lot of power to transfer by aerial cable. Where are those buckyball nanotube ropes when we need them?
And think of the tedium of winding in the ropes. or trying to recover them if they come down in the border areas. Gonna take a lot of cowboys to round up all that kite string.

Okay, but it's still 134,000 * 550 or 73 million ft-lbs per second.
If the wind is blowing up there at 100mph (146 feet/sec), the tension on the cable must be 73 million / 146 ft/sec or about 500,000 lbs.
Some cable.
A little web browsing shows a cable that can handle this tension with a safety factor of three is going to weigh about 8-10 pounds per foot. So if my math is right the poor kites have to be able to lift 450,000 pounds of line. Yipes.

I don't see many people analysing deeply the environmental impact of those technologies.
Suppose EVERYBODY started using wind and sea power... couldn't this change el niño's mood or something??
Possibly the impact is very weak, but I would like to see the figures.
And what about uniting the useful and the disagreeable? what about solar power centrals in the poles, where we are having already too much solar radiation???:)

What about using those high altitude blimps that we're going to put up there anyway to supply us with wireless broadband? That way the cable wouldn't have to be as strong, and therefore not as heavy. And if you made the weak point of the cable close-ish to the ground, most of a snapped cable would dangle from the blimp rather than fall to the ground.

The power is generated by the action of wind on the kite producing lift on half of the loop, and through manipulation of control surfaces, subsequent down-force on the other side of the loop. It's the mechanical conversion of wind-power that is harnessed here, so the simple lift generated by a blimp wouldn't work - how does it go down after it's ascent?

However, I think you'd be correct in another regard - having the kites anchored to a floating point (for example a blimp) would

Why don't you take a tethered blimp, and add an ordinary wind turbine? Somewhat less tension, It won't fall on your head, and you can put the generator up there too! (the cables only have to hold the thing in place, not transmit mechanical power)

A person can generate about 1/4 horsepower with an excersize bike. Given the daily rate for unskilled labor in many countries now, we could simply rig up a giant wheel like what Conan the Barbarian pushed around as a slave in that clearly prophetic movie.

Given the cost of building a nuke plant, then running it, getting rid of the waste, (hiding it really well for a really long time), and cleaning up after it -- it would be cheaper per kilowatt to simply have a bunch of low paid people push giant logs around in a circle.

The economics are outstanding. Its great excersize, and the power companies would be incented to provide health care at the same time. It provides plenty of jobs for unskilled labor, and could quickly be set up in the lowest income countries.

All in all, its a win-win. Best of all, it doesn't suffer from the one drawback everyone is clearly afraid to speak about with wind-power, which is the potential for slowing down the rotation of the earth! Clearly a danger if ever there was one. Why, if we slowed down the earth, and there was no centrifugal force apposing the gravity of our planet we would all be crushed! Oh the horror.

A person can generate about 1/4 horsepower with an excersize bike. Given the daily rate for unskilled labor in many countries now, we could simply rig up a giant wheel like what Conan the Barbarian pushed around as a slave in that clearly prophetic movie.

You're talking about outsourcing energy generation.

Bad idea.

Here in America, we've got a huge percentage of our population locked up in prisons. Let them do the hard work!

Pedal, you lazy dogs -- I said pedal! And get me another glass of lemon

This laddermill requires a lot of untested technology, and some of the problems don't seem to have been addressed at all (such as how the kites 'know' if they should be going up or down, how to make cables that never break but are light enough to lift, and how to stop the 'up' kites and 'down' kites colliding.

Given that all the down kites, and the up kites below the level of high winds are dead weight, wouldn't it make more sense to just put a big tethered autogyro or 10 on the cable instead, and drive a generator from the prop rotation? This would eliminate the dead weight, replace the unstable kites with fail-safe autogyros that land gently naturally, and changes the requirement for a flexible cable that can cope with extreme tension for a requirement for a weaker less flexible cable that can transmit electricity, which should be easier to produce.

The winds do not blow the same direction as you go higher. Sometimes you get 90 degree shear or 180 deg shear. The poor kites will always be doing a shuffle to work correctly and efficiently between the low-level, mid-level, and high-level winds. I think that this plan is how he plans to get his pies-in-the-sky......

Some of the parafoil kites I've owned would pick up a beer cooler but the concept seems kind of clumsy. A kite holding the top wheel of the loop that's being turned by smaller kites. Seems like a lot to go wrong. A wind turbine is pretty robust technology. The wind blows, blades turn, electricity comes out. Simple.

If height is the issue, then why not have a tethered blimp hoist wind turbines? You could even cover the top of the blimp with flexible solar panels and have a high-flying hybrid system and you don't have worry about bombing people with a giant bicycle wheel if the wind died. If the weather gets bad just reel the blimp in.

Use the pancake rotor types, carbon composite blades, you could make some pretty high production turbines that were light enough to be raised by a blimp. Some kind of frame and the tether could double as the transmission cable.

Oh no, not another wacko diversion from useful wind turbine design. I bet it'll make PopSci, just like all the other dumb energy things.

There was a similar idea to this about 20 years ago, called a "Lift Translator". It got goverment money. It made the cover of PopSci. It went precisely nowhere because it didn't work. This one's likely to work just as well/badly.

No-one I know in the wind energy industry thinks this 'laddermill" is remotely credible.

Professor Ockels says a few hundred of the installations, each requiring some 400 kites with 27ft wingspans, could generate enough electricity to supply the needs of a city the size of Seattle

"A few hundred"? That's at least 200, so we're talking about a minimum of 80,000, 27-foot kites, for a single large city. Then consider that each of these trains will be 5 miles long, and swaying in the wind. That means they need to stay some distance away from each other. My guess would be that half a mile between them (that's only 1/10th the length of a train) wouldn't be overly conservative. For a 14*14 installation (196 trains) that means just over 40 square miles (more than 25,000 acres) for a single installation. Sure, you can let some cows graze inbetween, but still. Somehow this whole scheme seems a little... impractical...

Several groups have been studying hanging kilometer long wires from satellites to generate energy for the satellite or space habitation. These operate on the same principle: exploit the electric field gradients in the earth's magnetosphere.
Several orbital experiments have been tried. I recall one time mechanical problems prevented full unwinding of the cable. Another time the cable shorted and burnt apart from a power surge. I suspects these bugs will be eventually fixed by the engineers.

I read the article and I guess there is a large wheel in the sky with a hub located maybe 5 miles high. From there is a closed loop cable to turn a turbine on the ground. How much does 10 miles of cable weigh since that wheel would have to support it. How would it be conected to this hub? I do not think by friction so there would have to be cogs on the cable and still there would be a need to maintain alot of force to keep the cable taut. It would have been nice if they could have a drawing of the syst

This is a really interesting concept. The designers say they won't fly the kite except in good weather so they won't have to worry about electrical storms etc. but I wonder if they have considered the atmosphere's natural electric field as well... It is estimated that the natural electric field potential between the earth's surface and the ionosphere is in the hundreds of thousands of volts range. While the current is usually very low for small but rather tall structures (regular kites, radio towers etc.) I would imagine that having a huge 5 mile wide kite 30 thousand!! feet up would make an immense difference in the current transmitted through a conducting wire to the ground. We may be talking about tens or perhaps even hundreds (??) of watts here. This will have to be dealt with and I imagine it could actually be used to perhaps, power some backup or secondary control equipment way up there.

I've heard suggestions like this many times. My main arguement is that we should consider how tapping energy from the atmospheric layers above the Earth may impact our global ecology. Would it pull more dust from space, creating heavier Coronal Mass Ejection saturation? Would it have any impact on the geodynamo? As wonderful as were the ideas of Nikola Tesla (who was among the first to consider tapping the atmosphere for electrical power) it is important to give these ideas thorough review.

"Professor Ockels says a few hundred of the installations, each requiring some 400 kites with 27ft wingspans, could generate enough electricity to supply the needs of a city the size of Seattle. The cost would be similar to that of generating power with polluting fossil fuels."

At a few hundred per city... that is a lot of kites..

Then you have to find the places to put them...

"The Laddermill would only be flown where aircraft are banned. One such area is the zone along the US-Mexican bo

Reminds me of something I saw when I was a kid. My dad and I were fishing off the coast of Cape Cod. The boat we were in was a 23' center console with twin 135hp engines. If memory serves me (this was some 25+ years ago) the boat would do about 40mph on a flat calm. Anyway... There was a good stiff breeze, good for sailing, kight flying, etc. At one point not too far in the distance we saw an orange kite flying in the sky. It was one of those $1.99 plastic things you can buy in any toy store. Well it didn't take us too long to realize that nobody was flying the kite because they'd have to be in the water given its location, and there weren't any other boats in the area. We decided to investigate (the fish weren't biting) so we headed towards the kite at full-throttle. It took us about 45 minutes but we eventually caught up with the kite. The string had apparently snapped or whoever was flying it had let go of the string. Enough string was dragging in the water to create just enough drag to keep the kite aloft, and the kite was dragging it through the water at a pretty decent speed. If the boat wasn't as fast as it was we probably wouldn't have caught the kite. We figured it could have made it all the way to Europe in a week or so if we let it. (Makes for a good story anyway) But it ended up in our closet instead.

I suppose as long as the kites in this ladder-thingy are designed properly they would continue to fly upright. But unless they have enough drag (like the string in my little tale) I'd suspect that the wind would just blow it out of the sky if the line were to break.